Speaker
Description
Synchrotron radiation is a ubiquitous mechanism linked to non-thermal emission across different bands of the electromagnetic spectrum from radio to x-rays and even γ-rays in a plethora of astro-physical sources ranging from supernova remnants to active galactic nuclei (AGN) and gamma-ray bursts (GRBs). A key physical parameter for the synchrotron emission of a single particle is the angle between it’s velocity v and the orientation of the magnetic field lines B. This is defined as the pitch-angle of the particle, denoted with α. When modeling this non thermal emission, isotropy of the emitting population across pitch-angles is assumed. Recent numerical results from particle in cell simulations (PIC), in environments of relativistic (σ0 ≫ 1) magnetic reconnection (RR) reveal that the derived distributions are inherently anisotropic in pitch-angle α. This anisotropy is imprinted as a broken power law of the mean square of pitch-angle sine α in the particle energy space ⟨sin2 α⟩ ∝ γ^m who’s slope is governed by the lepton magnetization σ0 and the ratio of the non-reconnecting to the reconnecting component of the magnetic field Bg/B0 Comisso and Jiang (2023). In this work we perform a comprehensive numerical study of the time-dependent evolution of a synchrotron emitting distribution by factoring in the dependence on pitch-angle. Contrary to previous works, we use a toy model inspired by the PIC results, to benchmark the initial particle distribution. We discuss the emerging slopes of the anisotropically cooled distribution as well as the new cooling break governing the cooling process and produce the spectra for the anisotropic fast and slow cooling regimes, as defined in the absence of an escape term. Finally we discuss the astrophysical implications of the anisotropy on the observed emitted spectra.